The main objective of this research is to develop and refine a new, noninvasive procedure for the detection and differential diagnosis of temporomandibular joint disorders, a prevalent class of disorders caused by any of several different underlying pathologies. The procedure, which we term Arthrophonometry measures the frictional losses of joint movements as revealed by their acoustical characteristics. Because the various diseases of the temporomandibular joint are characterized by different physical conditions (and consequently, different frictional losses), the associated joint sounds correspond categorically and uniquely to specific disease states. The acoustic analog of joint friction is mapped in relation to both the temporal and spatial properties of jaw movements and is further characterized using acoustic signal processing. The technique involved the placement of a vibration transducer over the areas of the temporomandibular joint and a lightweight magnet on the lower central incisors to record the bone-conducted joint sound and jaw movement, respectively. The sensors produce voltages that correspond to both the acoustic waveform radiated from the joint, and the position of the joing in space. These voltages are displayed simultaneously and graphically on a computer display terminal. The relationship between the acoustic markers and joint pathologies has been confirmed in preliminary studies by comparisons with conventional diagnostic methods and exploratory surgery. Existing techniques which are currently used for diagnosis of temporomandibular joint disorders are invasive, painful, and necessitate exposure to allergenic, iodine-containing contrast media, and substantial levels of radiation. Present methods are all hospital-based, personnel intensive, and expensive. The obvious advantages of Arthrophonometry are that it is non-invasive, non-allergenic, non-radiographic, painless, inexpensive, provides a permanent record, and allows for both diagnosis and assessment of therapeutic efficacy.